Removal of red tide organism by a novel cationic polymeric flocculant

摘要

Harmful algal blooms (HABs) occurring worldwide has posed severe threat to aquatic organisms,coastal aesthetics and public health.Currently,the usual remedial practice for cell removal in open water is to spread clay on the surface of seawater through the flocculation of alga and mineral particles.However,this study was made to synthesis a novel natural cationic polymeric flocculant grafted by quartemary ammonium monomer N-(3-chloro-2-hydroxypropyl) trimethyl ammonium chloride (CHPTAC) onto the backbone of corncob powder.The graft process was characterized by elemental analysis,Fourier-transform infrared spectrometer and scanning electron microscope techniques.A set of experiments were carried out to assess the feasibility of the flocculant to remove the dinoflagellate,Alexandrium tamarense.Results showed that after adding an aqueous slurry of 0.15 g·l-1,the seawater culture containing Alexandrium tamarens 104 cells ml-1 was removed by 70％ within 6 h.After an exposure period of 12 h,it was removed by 90％.Selection of monomer concentration in synthesis process,flocculant slurry aging time and the particle size of the flocculant were found to be important parameters affecting removal efficiency.These studies showed the cationic modified flocculant can be utilized as a promising substance for reducing adverse effects from harmful algal blooms in seawater,although considerable work remains before this approach can be used on natural open waters.